The following description relates to shimmy damping and, more specifically, to a maintenance free hydraulic shimmy damper.
A shimmy damper assembled to a landing gear unit of an aircraft operates by dissipating vibration energy induced during taxiing, landing and take-off procedures. For example, upper and lower torque links of a landing gear are typically connected to a shimmy damper and torsional vibration displacement from the proximal piston is transferred to an outer cylinder through the upper and lower torque links. The shimmy damper is mounted at the apex joint of the upper and lower torque links and provides damping to counteract the torsional vibration displacement.
A conventional shimmy damper includes a damping piston, a cylinder and a reservoir housing. The damping piston includes radial seals which define multiple chambers within the cylinder. Hydraulic oil flows from the reservoir housing to the multiple chambers through non-return valves. Damping is achieved by the viscous friction force when the hydraulic oil flows across the multiple chambers through a restrictor orifice in opposition to the torsional vibration displacement.
With the vibrational energy dissipated by the flow of hydraulic oil, the dissipated energy is converted into heat energy and causes a temperature of the damper to increase. Moreover, the high number of parts of the damper provides for increased numbers of failure modes and fluid leakage.